The mighty River Lune, flows down through the city of Lancaster and into Morecambe Bay. On its journey from its source in the Howgills, it passes through a land shaped by geology. Here there is a chance to see a geological process in the making. Further up the Lune Valley is limestone country, around Kirkby Lonsdale, Ease Gill, and the Three Peaks. These areas are famed for their caves, though for many of us, the wonders of the limestone world, are just words and pictures, though some of the wonders that you can see below ground, can be seen above it as well.
The cache co-ordinates take you to near the arches on the old railway bridge, just before the Millenium Bridge which crosses the lune. This option is easily accessible by wheelchairs, pushchairs, and those in mobility scooters. There is no need to climb over any railings or go near the river edge.
I want you to look at three of arches below the bridge. There are two which can be walked through, namely one which Damside Street, and another next to it. The third can be easily seen from the start of the Millenium Bridge.
The bridge used to carry a railway line which ran between Lancaster Castle Station and Green Ayre Station, the trackbed is now a footpath / cycleway. The bridge is made out of stones and bricks, though what we are interested in is the mor, or rather what has occured as a result of it. Mortar is traditionally a mix of lime and sand. Lime consists of calcium oxide, gained from heating limestone. At first there would have been neat lines of mortar between the sandstone blocks, but has time has gone on, and the structure has been exposed to water, the calcium oxide reacts with water to form calcium hydroxide. Over time, rainwater carries calcium hydroxide in a solution, which when it comes into contact with air, it reacts with carbon dioxide and calcium carbonate is preciptated.
In a cave the precipitation of calcium carbonate forms both staligtites and staligmites. Though in a location outwith of a cave, these deposits are known as calthemites. A calthemite is a deposit derived from concrete, lime or mortar, and they grow under man made structures, and look like cave structures.
Calthemites can appear in many forms, which are :
Flowstones, which looks like a flowing river off calcium carbonate, this tends to be rippled.
Straw Staligtites, which are long thin straw like structures.
Calthemite staligmites, which are a build up of calcium carbonate on the floor, which gradually gain height.
Calthemite rimstones, these form on the floor as a gradually sloping structure.
When a staligtite and staligmite join, it is known as a column.
This being an earthcache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please tell me what forms of calthemites you can see.
2. What colour are the calthemites, why is this?
3. Which arch has the most example of calthemites, what type is this? How long are these?
4. Please go to the second arch, the one which the pedestrian runs through, if you look up, you can see a type of calthemite, how long are these, and what is at their end?